Use the RAI manual as your MDS dictionary.
You can easily over- or undercode RUG drivers and quality indicators/ measures if you don't know the precise RAI definitions of various MDS items. Use this list of commonly misinterpreted terms as your guide:
Fever (J1h): A fever is present when the resident's temperature (°F) is 2.4 degrees greater than his baseline temperature. You can establish the baseline before the assessment reference date.
Falls (J4a and J4b): The distance to the next lower surface ... is not a factor in determining whether or not a fall occurred. If a resident rolled off a bed or mattress that was close to the floor, this is a fall. An intercepted fall is still a fall. A fall without injury is still a fall.
Urinary incontinence (H1b): If the resident's skin gets wet with urine, or if whatever is next to the skin (i.e., pad, brief, underwear) gets wet, count that as an episode of incontinence -- even if it's just a small volume of urine, for example, due to stress incontinence.
Pneumonia (I2e): Inflammation of the lungs; most commonly of bacterial or viral origin. Compare that to the definition for respiratory infection (I2f): Any upper or lower acute respiratory infection other than pneumonia.